Coherently pumped solitons in optical microresonators form as a result of the balance of the Kerr nonlinear shift and the cavity dispersion, as well as the parametric gain and the cavity loss. The soliton-forming mode family (in particular for bright solitons) in a microresonator must feature anomalous dispersion and minimal distortion of the dispersion (e.g., minimal avoided-mode-crossings). The power requirement for soliton operation is inversely proportional to the total Q factor of the mode family[1]}.
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